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37 Cards in this Set

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  • Back
Spleen white pulp at 5 wks gestation?
Primitive spleen arising from mesodermal tissue
Spleen white pulp at 13 wks gestation?
-- Lymphocytes and monocytes/macrophages

-- Presence of surface Ig on B-lymphocytes

-- Production of IgG and IgM Ab
Spleen white pulp at 6 mos gestation?
-- White pulp easily distinguished from red pulp

-- B-cells express surface IgM + autoimmune-assoc cross-reactive idiotypes
Spleen white pulp at birth?
primitive inactive follicles
Spleen white pulp 2-4 wks postpartum?
First primary follicles and dendritic cells

Germinal centers
Spleen red pulp at 8 wks gestation?
Thin-walled blood vessels form loops in the reticular cell meshwork of the promordial spleen
Spleen red pulp at 9 wks gestation?
Vascular loops evolve into distinct channels opening into endothelial-lined sinuses forming cords of Billroth
Filtering/Reservoir Fxn of the Spleen?
Large filter w/ strategically placed macrophages.

-- cleanses approx 4% of the blood volume per minute

-- removes old, damaged or abnormal RBCs from the circulation as well as excess mbrn and intracytoplasmic incusions from RBCs w/o lysis

-- Storage site for factor VIII and up to 1/3 of body's platelets, which can be released into circ under stress, or after epi injection
Immunologic Fxn of the Spleen?
Complex system specializing in interaction btwn Ag-presenting cells, and rare, Ag-specific lymphocytes resulting in lifelong immunity
3 elements of spleen's immune fxn?
1. phagocytosis and clearance of unopsonized particulate matter

2. specific immune responses

3. production and processing of opsonins (tufsin and properdin)

Site for early IgM response. Role somewhat limited in Ab responses to i.m. or subQ injected Ag, but essential to early body response to i.v. Ag
Regenerative fxn of the spleen?
Stem-cell populations found in spleen can differentiate into cells of other organs

Also reserve population of hematopoietic cells can be tapped when BM cannot fully meet body's demand
Criteria for splenomegaly on plain film?
Considered enlarged if it is

>6cm long OR

length x width = >75cm

NORMAL if not seen on abdom plain film or if less than 85% kidney size
Criteria for splenomegaly on ultrasound?
Enlarged if:

≥ 13cm in length OR

≥ 5cm in thickness
Criteria for splenomegaly on liver and spleen scan?
Enlarged if:

posterior length is >14cm OR

lateral scan area exceeds 80cm2
What is hyperspenism?
A clinical syndrome characterized by:
-- splenomegaly AND
-- assoc destruction of one or more cell lines in the peripheral blood.

**Often present in pts w/ very large spleens
Important Hx of pt w/ splenomegaly?
past medical illness
exposure to carcinogens or other environmental hazards
drinking, smoking, drug use
recent travel
systemic symptoms: fever, night sweats, weight loss
Important PE features of pt w/ splenomegaly?
peripheral edema
In the CBC, if you find neutropenia, anemia, and/or thrombocytopenia as a consequence of spleen trapping, this means the pt likely has...?
In the CBC, if you find the pt has neutrophilia + left shift, this means the pt likely has...?
In a peripheral blood smear, invading orgs in RBCs are indicators of...?
In a peripheral blood smear, invading orgs in PMNs or monocytes are indicators of...?
In a peripheral blood smear, findings of toxic granulations, Dohle bodies, vacuoles in PMNs, and fragmented RBCs, means the pt likely has...?
overwhelming sepsis
In the peripheral blood smear, nucleated RBCs + teardrop-shaped RBCs means the pt likely has...?
Bone marrow invasion
In the peripheral blood smear, immature WBCs or blasts means the pt likely has...?
hematologic malignancy
When might a splenectomy be warranted?
immune thrombocytopenia
RBC mbrn defects
Immune deficiency
Storage disease
Causes of fxnal hyposplenism?
sickle cell hemoglobinopathies
irradiation to ULQ
Chronic inflamm diseases
--Celiac disease
Acute alcoholism
Extensive GVHD
Overload of RES fxn
How are filtering and reservoir fxns affected in a pt w/ asplenia/hyposplenia?
1. increased numbers leukocytes and platelets

2. RBC inclusions on peripheral smear (Howell-Jolly bodies)

3. Increase number of RBC "pits" on interference microscopy

4. poor uptake of technetium on spleen scans
How is immunologic fxn affected in a pt w/ asplenia/hyposplenia?
OVERWHELMING INFECTION to encapsulated bacteria
-- S. pneumo
-- H. flu
-- N. meningitides

Other orgs such as E.coli, S.aureus, group B strep, and P.aeruginosa have also, to a lesser degree, been responsible for fulminant infections in asplenic pts

Infants/young children -- lack exposure to these bacteria and have to rely to a greater degree on splenic sequestration and clearance

Adults -- risk of infection related to overall ↓ Ab production and splenic clearance
What are the risk factors for overwhelming infection post-splenectomy (OPSI)?
AGE: Children <15 have ↑ overall risk compared to adults; highest rate in infants/young children

TIME INTERVAL: ↑ during first 2 yrs post-splenectomy (50-70% of all OPSI) and more so in young children. Risk is lifelong.

--trauma -- infection rate in adults similar to gen pop but 58times more fatal
--hematologic d/o -- highest rate and ↑ w/ severe immune impairment
What are the classic symptoms of OPSI?
brief prodrome of fever of only few hours duration w/ mild unspecific symptoms
- headache
- malaise
- nausea
- vomiting
- diarrhea
- chills
- abdom pain

Rapidly evolves into septoc shock; generally no evidence of localized infection

DIC in 50-75%

If not treated promptly -- death w/in 48-72h

Fully developed OPSI has mortality of 75%
What clinical/lab testing should one get with possible OPSI?
Should have high index of suspicion:
- cultures and gram stains (blood, urine, sputum, and CSF in children and infants)
- CBC, serum chem
- chest radiograph
- evaluate periph smears for bacterial and Howell-Jolly bodies
- immed institution of empirical antiobiotherapy active against PCN-R pneumococci and b-lactamase-producing orgs after cultures obtained
Protective immunization for OPSI?
Highly immunogenic capsular vaccines are available for the three major orgs:
1. Strep pneumo (23PS and PCV7)
2. H. flu type B
3. N. meningitides (groups A,C,Y and W135)
Indications for protective immunization for OPSI?
1. At least 14 days before splenectomy or immediately after if performed emergently

2. All children ≤23mo should receive PCV7 and Hib per AAP recommendations

3. High risk children 24-59mos for invasive pneumococcal infection should receive PCV7.
- sickle cell
- congenital or acquired asplenia
- splenic dysfxn
- congenital immune defic
- chronic cardiac disease
- chronic pulm disease
- CSF leaks
- chronic renal insuff
- Pts undergoing chemo, radiation, and solid organ transplantaion
- DM
What role does antibiotic chemoprophylaxis play?
Impt in early years after splenectomy in peds pts when the risk of overwhelming infection is the greatest
**WILL NOT prevent against PCN-R orgs
Alt strategies proposed for prophylaxis of OPSI?
1. daily proph during first two uears after splenectomy

2. In pts w/ sickle cell, daily proph until age 5/6

3. Give supply of antipneumococcal Ab to asplenic pts to start empirically for febrile illness followed by rapid eval by a physician

4. rapid eval by physician followed by admin of parenteral antibiotics
What are some methods use to salvage splenic fxn?
splenic artery ligation or embolization

splenic repair

partial splenectomy

implantation of splenic tissue

Splenic fxn better preserved in:
partial splen/repair > implantation > artery ligation
How should one educate a patient that is post-splenectomy/hyposplenic?
1. info about altered immune system

2. importance of seeking eval for any febrile illness, no matter how mild the symptoms

3. use medic-alert or similar

4. should not be kept waiting in ER triage or wait days before seeing physician

5. Tx should be administered empirically

6. Asplenic pts traveling to endemic areas for malaria and babesia should be cautioned about increased risk